Hillary Clinton just had her toughest grilling yet

Former Secretary of State Hillary Clinton's Sunday "Meet the
Press" interview featured question after question on her email
use at the State Department.

Host Chuck Todd asked the Democratic presidential front-runner
roughly a dozen inquiries about the controversy — before moving
on to questions about her sinking poll numbers and policy
flip-flops over the years.

Todd began the interview by playing a seven-year-old clip of
Clinton saying she wants "a much more transparent government."

He suggested that it might have been hypocritical for Clinton to
exclusively use a private email account while she was at the
State Department — placing her messages outside of
government archives.

But Clinton argued that she actually went out of her way to
include government email addresses in her work-related
communications.

"All of the emails that I sent were intended to be in the
government system if they were work-related," she said. "If I had
to do it all over again, I would have used a separate email
account. I did it for convenience, and it turned out not to be
that at all."

Clinton also said her team conducted a "careful review" and
turned all of her work-related emails over to government
archivists. But Todd then pressed Clinton twice about a
report last week that she
failed to turn over an email chain with former commander
of US Central Command David Petraeus, which challenged the
completeness of her records.

"The reason that we know about the email chain with Gen. Petraeus
is because it was on a government server," Clinton responded
without offering a specific explanation for the discrepancy. "We
had a very thorough review process that we conducted. And my
attorney supervised it. They went through everything."

Todd went on to press Clinton on the elaborate amount of work
needed to set up a personal email server, how practical it was to
rely on recipients' government email addresses for archiving
purposes, and a
recent Washington Post report on the differences between how
she and the State Department describe the department's initial
request that she turn over her emails.

"Perhaps the reason you wanted to have a private server and not a
government server is that Republicans have been coming after you
for years. You might have been running for president in the
future, and you wanted to make it a little more difficult for
congressional investigators to subpoena your government emails
and a little more difficult for Freedom of Information Act
requests. Is that a fair theory or not?" Todd asked.

Clinton called Todd's theory "totally ridiculous" and that it
"never crossed my mind."

Chuck Todd interviews
Hillary Clinton.NBC/screengrab

Clinton's presidential campaign has been battered for months by critical
headlines about her email use and her decision to delete the
entire email trove after turning over the messages deemed
work-related to the government.

Clinton insists she did not jeopardize sensitive information, for
which she said she used secure channels. But the FBI reportedly
took control of the server to look into whether any material was
mishandled in connection to the account.

And, as Todd noted, the story doesn't seem to be going away.

"There's an allegation about your email server. The campaign
provides an explanation. You provide an explanation. There's a
new allegation. You have to provide a new explanation. There's an
addendum to that explanation. It has the feel of a 'drip, drip,
drip.' Can you reassure Democrats that there's nothing else
here?" Todd asked.

Clinton agreed but said there is only so much she could do to
reassure people concerned about the evolving story line.

"Well, it is like a drip, drip, drip," she said. "I want these
questions to be answered. I can't predict to you what the
Republicans will come up with — what kind charges or claims they
might make. I have no control over that. I can only do the best I
can to try to respond."

Todd responded by asking if she could "say with 100% certainty
that the deleted emails that the FBI's not going to find anything
in there that's going to cause you to have to explain again?"

Clinton suggested she couldn't be that certain.

"All I can tell you is that when my attorneys conducted this
exhaustive process. I did not participate," she said.

Later in the interview, Todd asked Clinton how she treated emails
related to her family foundation and how the controversy
damaged her standing in the polls. Sen. Bernie Sanders
(I-Vermont), running as a Democrat, has surged in early-state surveys, while Vice
President Joe Biden, who is still weighing run, already
has a solid base of support.

Todd also played a montage of Clinton's flip-flops on issues
over the years — including her vote on the 2003 invasion of Iraq
that she later admitted was a mistake, her past opposition to
same-sex marriage, and her statement that she was "inclined" to
support the Keystone XL Pipeline to which she recently
announced her opposition.

"I can just tell you that I am not someone who stakes out a
position and holds it regardless of the evidence," Clinton said
after offering a point-by-point defense of her policy shifts.